Melt blending of polylactide and linear lowdensity polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactidepolyethylene (PLLA-PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA-PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA-PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE.

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The regioselective functionalization of both model and commercial polypropylenes of varying tacticity has been conducted by a rhodium-catalyzed functionalization of the methyl C-H bonds of the polymer with diboron reagents. Rhodium-catalyzed borylation of the polypropylenes, followed by oxidation of the boron-containing material, produced polymers containing 0.2-1.5% hydroxymethyl side chains. Both the number-average molecular weights and molecular weight distributions of the polypropylenes were essentially unchanged after the catalytic and oxidative functionalization process. The efficiency of the borylation process was affected by the molecular weight of the polymer, the steric hindrance around the methyl groups, and the ratio of the diboron reagent to the monomer repeat unit. The hydroxylated derivative of the commercial isotactic polypropylene was used as macroinitiator for the aluminum-mediated ring-opening polymerization of epsilon-caprolactone to prepare polypropylene-graft-polycaprolactone. This graft copolymer was an effective compatibilizer for melt blends of polypropylene and polycaprolactone.